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Cost Effective Open Geometry HTS MRI System amended to BSCCO 2212 Wire for High Field Magnets

Description: The original goal of this Phase II Superconductivity Partnership Initiative project was to build and operate a prototype Magnetic Resonance Imaging (MRI) system using high temperature superconductor (HTS) coils wound from continuously processed dip-coated BSCCO 2212 tape conductor. Using dip-coated tape, the plan was for MRI magnet coils to be wound to fit an established commercial open geometry, 0.2 Tesla permanent magnet system. New electronics and imaging software for a prototype higher field superconducting system would have added significantly to the cost. However, the use of the 0.2 T platform would allow the technical feasibility and the cost issues for HTS systems to be fully established. Also it would establish the energy efficiency and savings of HTS open MRI compared with resistive and permanent magnet systems. The commercial goal was an open geometry HTS MRI running at 0.5 T and 20 K. This low field open magnet was using resistive normal metal conductor and its heat loss was rather high around 15 kolwatts. It was expected that an HTS magnet would dissipate around 1 watt, significantly reduce power consumption. The SPI team assembled to achieve this goal was led by Oxford Instruments, Superconducting Technology (OST), who developed the method of producing commercial dip coated tape. Superconductive Components Inc. (SCI), a leading US supplier of HTS powders, supported the conductor optimization through powder optimization, scaling, and cost reduction. Oxford Magnet Technology (OMT), a joint venture between Oxford Instruments and Siemens and the world’s leading supplier of MRI magnet systems, was involved to design and build the HTS MRI magnet and cryogenics. Siemens Magnetic Resonance Division, a leading developer and supplier of complete MRI imaging systems, was expected to integrate the final system and perform imaging trials. The original MRI demonstration project was ended in July 2004 by mutual consent of Oxford ...
Date: August 11, 2006
Creator: Marken, Kennth
Partner: UNT Libraries Government Documents Department

Final Report: Characterization of Hydrogen Adsorption in Carbon-Based Materials by NMR

Description: In support of DOE/EERE's Fuel Cell Technologies Program Hydrogen Sorption Center of Excellence (HSCoE), UNC conducted Nuclear Magnetic Resonance (NMR) measurements that contributed spectroscopic information as well as quantitative analysis of adsorption processes. While NMR based Langmuir isotherms produce reliable H2 capacity measurements, the most astute contribution to the center is provided by information on dihydrogen adsorption on the scale of nanometers, including the molecular dynamics of hydrogen in micropores, and the diffusion of dihydrogen between macro and micro pores. A new method to assess the pore width using H2 as probe of the pore geometry was developed and is based on the variation of the observed chemical shift of adsorbed dihydrogen as function of H2 pressure. Adsorbents designed and synthesized by the Center were assessed for their H2 capacity, the binding energy of the adsorption site, their pore structure and their ability to release H2. Feedback to the materials groups was provided to improve the materials’ properties. To enable in situ NMR measurements as a function of H2 pressure and temperature, a unique, specialized NMR system was designed and built. Pressure can be varied between 10-4 and 107 Pa while the temperature can be controlled between 77K and room temperature. In addition to the 1H investigation of the H2 adsorption process, NMR was implemented to measure the atomic content of substituted elements, e.g. boron in boron substituted graphitic material as well as to determine the local environment and symmetry of these substituted nuclei. The primary findings by UNC are the following: • Boron substituted for carbon in graphitic material in the planar BC3 configuration enhances the binding energy for adsorbed hydrogen. • Arrested kinetics of H2 was observed below 130K in the same boron substituted carbon samples that combine enhanced binding energy with micropore structure. • Hydrogen storage material ...
Date: July 11, 2011
Creator: Wu, Yue & Kleinhammes, Alfred
Partner: UNT Libraries Government Documents Department

Numerical Algorithms for Two-Dimensional Dry Granular Flow with Deformable Elastic Grain

Description: The authors consider the dynamics of interacting elastic disks in the plane. This is an experimentally realizable two-dimensional model of dry granular flow where the stresses can be visualized using the photoelastic effect. As the elastic disks move in a vacuum, they interact through collisions with each other and with the surrounding geometry. Because of the finite propagation speed of deformations inside each grain it can be difficult to capture computationally even simple experiments involving just a few interacting grains. The goal of this project is to improve our ability to simulate dense granular flow in complex geometry. They begin this process by reviewing some past work, how they can improve upon previous work. the focus of this project is on capturing the elastic dynamics of each grain in an approximate, computationally tractable, model that can be coupled to a molecular dynamics scheme.
Date: August 11, 2005
Creator: Boateng, H A; Elander, V; Jin, C; Li, Y; Vasquez, P & Fast, P
Partner: UNT Libraries Government Documents Department

Final Report: A Transport Phenomena Based Approach to Probe Evolution of Weld Macro and Microstructures and A Smart Bi-directional Model of Fusion Welding

Description: In recent years, applications of numerical heat transfer and fluid flow models of fusion welding have resulted in improved understanding of both the welding processes and welded materials. They have been used to accurately calculate thermal cycles and fusion zone geometry in many cases. Here we report the following three major advancements from this project. First, we show how microstructures, grain size distribution and topology of welds of several important engineering alloys can be computed starting from better understanding of the fusion welding process through numerical heat transfer and fluid flow calculations. Second, we provide a conclusive proof that the reliability of numerical heat transfer and fluid flow calculations can be significantly improved by optimizing several uncertain model parameters. Third, we demonstrate how the numerical heat transfer and fluid flow models can be combined with a suitable global optimization program such as a genetic algorithm for the tailoring of weld attributes such as attaining a specified weld geometry or a weld thermal cycle. The results of the project have been published in many papers and a listing of these are included together with a list of the graduate thesis that resulted from this project. The work supported by the DOE award has resulted in several important national and international awards. A listing of these awards and the status of the graduate students are also presented in this report.
Date: December 11, 2009
Creator: DebRoy, Dr. Tarasankar
Partner: UNT Libraries Government Documents Department

Status report on high fidelity reactor simulation.

Description: This report presents the effort under way at Argonne National Laboratory toward a comprehensive, integrated computational tool intended mainly for the high-fidelity simulation of sodium-cooled fast reactors. The main activities carried out involved neutronics, thermal hydraulics, coupling strategies, software architecture, and high-performance computing. A new neutronics code, UNIC, is being developed. The first phase involves the application of a spherical harmonics method to a general, unstructured three-dimensional mesh. The method also has been interfaced with a method of characteristics. The spherical harmonics equations were implemented in a stand-alone code that was then used to solve several benchmark problems. For thermal hydraulics, a computational fluid dynamics code called Nek5000, developed in the Mathematics and Computer Science Division for coupled hydrodynamics and heat transfer, has been applied to a single-pin, periodic cell in the wire-wrap geometry typical of advanced burner reactors. Numerical strategies for multiphysics coupling have been considered and higher-accuracy efficient methods proposed to finely simulate coupled neutronic/thermal-hydraulic reactor transients. Initial steps have been taken in order to couple UNIC and Nek5000, and simplified problems have been defined and solved for testing. Furthermore, we have begun developing a lightweight computational framework, based in part on carefully selected open source tools, to nonobtrusively and efficiently integrate the individual physics modules into a unified simulation tool.
Date: December 11, 2006
Creator: Palmiotti, G.; Smith, M.; Rabiti, C.; Lewis, E.; Yang, W.; Leclere,M. et al.
Partner: UNT Libraries Government Documents Department

Minimum Critical Values Study

Description: This report provides minimum critical values for various 30-cm water-reflected uranium and plutonium oxide and nitrate aqueous mixtures as calculated by the SCALE CSAS1X sequence using the 238-group ENDF/B-V neutron cross-section library. The minimum values were determined through parametric searches in one-dimensional geometry. The calculations have been performed to obtain the minimum values: critical volume and mass for spheres, critical radius for cylinders, critical thickness for slabs, and minimum critical concentration (infinite geometry) for the following homogeneous mixtures: (1) UO{sub 2}-H{sub 2}O for 3, 4, 5, 20, and 100 wt % {sup 235}U; (2) UNH for 3, 4, 5, 20, and 100 wt % {sup 235}U; (3) PuO{sub 2}-H{sub 2}O for 100/0/0, 95/5/0, 90/5/5, 80/10/10, and 71/17/11/1 wt % of {sup 239}Pu/{sup 240}Pu/{sup 241}Pu(/{sup 242}Pu); and (4) PuNH for 100/0/0, 95/5/0, 90/5/5, 80/10/10, and 71/17/11/1 wt % of {sup 239}Pu/{sup 240}Pu/{sup 241}Pu(/{sup 242}Pu). All bounding surfaces were fully reflected by 30 cm of H{sub 2}O.
Date: July 11, 2005
Creator: Fox, P.B.
Partner: UNT Libraries Government Documents Department

NIMROD Resistive Magnetohydrodynamic Simulations of Spheromak Physics

Description: The physics of spheromak plasmas is addressed by time-dependent, three-dimensional, resistive magneto-hydrodynamic simulations with the NIMROD code. Included in some detail are the formation of a spheromak driven electrostatically by a coaxial plasma gun with a flux-conserver geometry and power systems that accurately model the Sustained Spheromak Physics Experiment (SSPX) (R. D. Wood, et al., Nucl. Fusion 45, 1582 (2005)). The controlled decay of the spheromak plasma over several milliseconds is also modeled as the programmable current and voltage relax, resulting in simulations of entire experimental pulses. Reconnection phenomena and the effects of current profile evolution on the growth of symmetry-breaking toroidal modes are diagnosed; these in turn affect the quality of magnetic surfaces and the energy confinement. The sensitivity of the simulation results address variations in both physical and numerical parameters, including spatial resolution. There are significant points of agreement between the simulations and the observed experimental behavior, e.g., in the evolution of the magnetics and the sensitivity of the energy confinement to the presence of symmetry-breaking magnetic fluctuations.
Date: December 11, 2007
Creator: Hooper, E B; Cohen, B I; McLean, H S; Wood, R D; Romero-Talamas, C A & Sovinec, C R
Partner: UNT Libraries Government Documents Department

Probing AGN Broad Line Regions With LAT Observations of FSRQs

Description: The GLAST Large Area Telescope (LAT) is expected to detect gamma-ray emission from over a thousand active galaxies, many of which will be flat spectrum radio quasars (FSRQs). A commonly assumed ingredient of leptonic models of FRSQs is the contribution to the gamma-ray flux from external inverse-Compton (EIC) scattering of photons from the broad line region (BLR) material by relativistic electrons and positrons in the jet. Here we explore the effect of the BLR geometry on the high-energy emission from FSRQs.
Date: October 11, 2007
Creator: Carson, Jennifer E.; Chiang, James; /SLAC; Bottcher, Markus & U., /Ohio
Partner: UNT Libraries Government Documents Department

Highly Fluorescent Group 13 Metal Complexes with Cyclic, Aromatic Hydroxamic Acid Ligands

Description: The neutral complexes of two ligands based on the 1-oxo-2-hydroxy-isoquinoline (1,2-HOIQO) motif with group 13 metals (Al, Ga, In) show bright blue-violet luminescence in organic solvents. The corresponding transition can be attributed to ligand-centered singlet emission, characterized by a small Stokes shifts of only a few nm combined with lifetimes in the range between 1-3 ns. The fluorescence efficiency is high, with quantum yields of up to 37% in benzene solution. The crystal structure of one of the indium(III) complexes (trigonal space group R-3, a = b = 13.0384(15) {angstrom}, c = 32.870(8) {angstrom}, ? = {beta} = 90{sup o}, {gamma} = 120{sup o}, V = 4839.3(14) {angstrom}{sup 3}, Z = 6) shows a six-coordinate geometry around the indium center which is close to trigonal-prismatic, with a twist angle between the two trigonal faces of 20.7{sup o}. Time-dependent density functional theory (TD-DFT) calculations (Al and Ga: B3LYP/6-31G(d)); In: B3LYP/LANL2DZ of the fac and mer isomers with one of the two ligands indicate that there is no clear preference for either one of the isomeric forms of the metal complexes. In addition, the metal centers do not have a significant influence on the electronic structure, and as a consequence, on the predominant intraligand optical transitions.
Date: February 11, 2008
Creator: Seitz, Michael; Moore, Evan G. & Raymond, Kenneth N.
Partner: UNT Libraries Government Documents Department

A Qualitative Investigation of Deposition Velocities of a Non-Newtonian Slurry in Complex Pipeline Geometries

Description: The External Flowsheet Review Team (EFRT) has identified the issues relating to the Waste Treatment and Immobilization Plant (WTP) pipe plugging. Per the review’s executive summary, “Piping that transports slurries will plug unless it is properly designed to minimize this risk. This design approach has not been followed consistently, which will lead to frequent shutdowns due to line plugging.” To evaluate the potential for plugging, testing was performed to determine critical velocities for the complex WTP piping layout. Critical velocity is defined as the point at which a moving bed of particles begins to form on the pipe bottom during slurry-transport operations. Pressure drops across the fittings of the test pipeline were measured with differential pressure transducers, from which the critical velocities were determined. A WTP prototype flush system was installed and tested upon the completion of the pressure-drop measurements. We also provide the data for the overflow relief system represented by a WTP complex piping geometry with a non-Newtonian slurry. A waste simulant composed of alumina (nominally 50 μm in diameter) suspended in a kaolin clay slurry was used for this testing. The target composition of the simulant was 10 vol% alumina in a suspending medium with a yield stress of 3 Pa. No publications or reports are available to confirm the critical velocities for the complex geometry evaluated in this testing; therefore, for this assessment, the results were compared to those reported by Poloski et al. (2008) for which testing was performed for a straight horizontal pipe. The results of the flush test are compared to the WTP design guide 24590-WTP-GPG-M-0058, Rev. 0 (Hall 2006) in an effort to confirm flushing-velocity requirements.
Date: May 11, 2009
Creator: Yokuda, Satoru T.; Poloski, Adam P.; Adkins, Harold E.; Casella, Andrew M.; Hohimer, Ryan E.; Karri, Naveen K. et al.
Partner: UNT Libraries Government Documents Department

Qualification of Automated Low-Field NMR Relaxometry for Quality Control of Polymers in a Production Setting

Description: Implementation of a low field time-domain NMR scanner as a diagnostic tool in the production of new polymer components is described in the context of qualification of a new QA/QC device. A study to determine the optimal experimental parameters was performed and a robotic autosampler was built to enable scanning of multiple pads. Relationships between T{sub 2} values and physical properties of DC745 slabs were investigated, and the appropriate sampling parameters for the production setting were determined. Two versions of a robotic autosampler were built, and for the component described here a fourth radial axis was required in addition to traditional X, Y, and Z movement to eliminate the large variability in T{sub 2} due to inconsistent sample coverage caused by complex rib geometry of the component. Data show that with appropriate choice of experimental conditions of the NMR detector and the detection geometry of the robotic autosampler, sufficient resolution of variations in crosslink density on the millimeter scale could be determined. All data to date demonstrates that low-field NMR devices are a feasible tool for use in production settings for non-destructive quality control of polymer components.
Date: May 11, 2007
Creator: Chinn, S; Cook-Tendulkar, A; Maxwell, R; Wheeler, H; Wilson, M & Xie, Z
Partner: UNT Libraries Government Documents Department

The Affect of Realistic Geologic Heterogeneity on Local and Regional P/S Amplitude Ratios Based on Numerical Simulations

Description: Regional seismic discriminants based on high-frequency P/S ratios reliably distinguish between earthquakes and explosions. However, P/S discriminants in the 0.5 to 3 Hz band (where SNR can be highest) rarely perform well, with similar ratios for earthquake and explosion populations. Variability in discriminant performance has spawned numerous investigations into the generation of S-waves from explosions. Several viable mechanisms for the generation of S-waves from explosions have been forwarded, but most of these mechanisms do not explain observations of frequency-dependant S-wave generation. Recent studies have focused on the affect of near-source scattering to explain the frequency-dependence of both S-wave generation and P/S discriminant performance. In this study we investigate near-source scatter through numerical simulation with a realistic geological model We have constructed a realistic, 3-dimensional earth model of the southern Basin and Range. This regional model includes detailed constraints at the Nevada Test Site (NTS) based on extensive geologic and geophysical studies. Gross structure of the crust and upper mantle is taken from regional surface-wave studies. Variations in crustal thickness are based on receiver function analysis and a compilation of reflection/refraction studies. Upper-crustal constraints are derived from geologic maps and detailed studies of sedimentary basin geometry throughout the study area. The free surface is based on a 10-meter digital elevation model (DEM) at NTS, and a 60-meter DEM elsewhere. The model extends to a depth of 150km, making it suitable for simulations at local and regional distances. Our simulation source is based on the 1993 Non-Proliferation Experiment explosion at the NTS. This shot was well recorded, offering ample validation data. Our validation tests include measures of long-period waveform fit and relative amplitude measurements for P and S phases. Our primary conclusion is that near-source topography and geologic complexity in the upper crust strongly contributed to the generation of S-waves from the ...
Date: July 11, 2005
Creator: Myers, S C; Wagoner, J L; Preston, L; Smith, K & Larsen, S C
Partner: UNT Libraries Government Documents Department

Crystallization Behavior of Virgin TR-55 Silicone Rubber Measured Using Dynamic Mechanical Thermal Analysis with Liquid Nitrogen Cooling

Description: Dynamic mechanical thermal analysis (DMTA) of virgin TR-55 silicone rubber specimens was conducted. Two dynamic temperature sweep tests, 25 to -100 C and 25 to -70 to 0 C (ramp rate = 1 C/min), were conducted at a frequency of 6.28 rad/s (1 Hz) using a torsion rectangular test geometry. A strain of 0.1% was used, which was near the upper limit of the linear viscoelastic region of the material based on an initial dynamic strain sweep test. Storage (G{prime}) and loss (G{double_prime}) moduli, the ratio G{double_prime}/G{prime} (tan {delta}), and the coefficient of linear thermal expansion ({alpha}) were determined as a function of temperature. Crystallization occurred between -40 and -60 C, with G{prime} increasing from {approx}6 x 10{sup 6} to {approx}4 x 10{sup 8} Pa. The value of {alpha} was fairly constant before ({approx}4 x 10{sup -4} mm/mm- C) and after ({approx}3 x 10{sup -4} mm/mm- C) the transition, and peaked during the transition ({approx}3 x 10{sup -3} mm/mm- C). Melting occurred around -30 C upon heating.
Date: February 11, 2010
Creator: Small IV, W & Wilson, T S
Partner: UNT Libraries Government Documents Department

Searching for optimal mitigation geometries for laser resistant multilayer high reflector coatings

Description: Growing laser damage sites on multilayer high reflector coatings can limit mirror performance. One of the strategies to improve laser damage resistance is to replace the growing damage sites with pre-designed benign mitigation structures. By mitigating the weakest site on the optic, the large aperture mirror will have a laser resistance comparable to the intrinsic value of the multilayer coating. To determine the optimal mitigation geometry, the finite difference time domain method (FDTD) was used to quantify the electric-field intensification within the multilayer, at the presence of different conical pits. We find that the field intensification induced by the mitigation pit is strongly dependent on the polarization and the angle of incidence (AOI) of the incoming wave. Therefore the optimal mitigation conical pit geometry is application specific. Furthermore, our simulation also illustrates an alternative means to achieve an optimal mitigation structure by matching the cone angle of the structure with the AOI of the incoming wave, except for the p-polarization wave at a range of incident angles between 30{sup o} and 45{sup o}.
Date: February 11, 2011
Creator: Qiu, S R; Wolfe, J E; Monterrosa, A M; Feit, M D; Pistor, T V & STolz, C J
Partner: UNT Libraries Government Documents Department

Toward Interoperable Mesh, Geometry and Field Components for PDE Simulation Development

Description: Mesh-based PDE simulation codes are becoming increasingly sophisticated and rely on advanced meshing and discretization tools. Unfortunately, it is still difficult to interchange or interoperate tools developed by different communities to experiment with various technologies or to develop new capabilities. To address these difficulties, we have developed component interfaces designed to support the information flow of mesh-based PDE simulations. We describe this information flow and discuss typical roles and services provided by the geometry, mesh, and field components of the simulation. Based on this delineation for the roles of each component, we give a high-level description of the abstract data model and set of interfaces developed by the Department of Energy's Interoperable Tools for Advanced Petascale Simulation (ITAPS) center. These common interfaces are critical to our interoperability goal, and we give examples of several services based upon these interfaces including mesh adaptation and mesh improvement.
Date: July 11, 2005
Creator: Chand, K K; Diachin, L F; Li, X; Ollivier-Gooch, C; Seol, E S; Shephard, M et al.
Partner: UNT Libraries Government Documents Department

Near Edge X-Ray Absorption Fine Structure Spectroscopy with X-Ray Free-Electron Lasers

Description: We demonstrate the feasibility of Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy on solids by means of femtosecond soft x-ray pulses from a free-electron laser (FEL). Our experiments, carried out at the Free-Electron Laser at Hamburg (FLASH), used a special sample geometry, spectrographic energy dispersion, single shot position-sensitive detection and a data normalization procedure that eliminates the severe fluctuations of the incident intensity in space and photon energy. As an example we recorded the {sup 3}D{sub 1} N{sub 4,5}-edge absorption resonance of La{sup 3+}-ions in LaMnO{sub 3}. Our study opens the door for x-ray absorption measurements on future x-ray FEL facilities.
Date: December 11, 2009
Creator: Bernstein, D.P.; Acremann, Y.; Scherz, A.; Burkhardt, M.; Stohr, J.; /SLAC et al.
Partner: UNT Libraries Government Documents Department

An Analytical Modeling Method for Calculating the Current Delivery Capacity of a Thin-Film Cathode and the Stability of Localized Corrosion Under Atmospheric Environemnts

Description: Corrosion resistant materials under atmospheric conditions can suffer from localized corrosion (e.g., pitting, crevice, stress-corrosion cracking). The stability of such a localized corrosion site requires that the site (anode) must dissolve at a sufficiently high rate to maintain the critical chemistry and that it be coupled to a wetted surrounding area (cathode) that can provide a matching cathodic current. The objectives of this study were to computationally characterize the stability of such a local corrosion system and to explore the effects of physiochemical and electrochemical parameters. The overall goal of the work is to contribute to the establishment of a scientific basis for the prediction of the stabilization of localized attack. An analytical method is presented for evaluating the stability of localized corrosion of corrosion-resistant alloys under thin-layer (or atmospheric) conditions. The method requires input data that are either thermodynamic in nature or easily obtained experimentally. The maximum cathode current available depends on the cathode geometry, temperature, relative humidity, deposition density of salt (i.e., mass of salt per unit area of cathode), and interfacial electrochemical kinetics. The anode demand depends on the crevice geometry, the position of attack within the crevice, and the localized corrosion stability product. The localized corrosion stability product, i*x, is the product of the current density at the localized corrosion site and the depth of that localized corrosion site. By coupling these two approaches for analysis of the current capacity of the cathode and the current demand of the anode, the stability of a crevice can be determined for a given environmental scenario. The method has been applied to the atmospheric localized corrosion of Type 31GL stainless steel as well as Alloy C-22. The effects of the key parameters are described and compared.
Date: October 11, 2006
Creator: Chen, Z.Y. & Kelly, R.G.
Partner: UNT Libraries Government Documents Department

Dissecting the Gravitational Lens B1608 656. II. Precision Measurements of the Hubble Constant, Spatial Curvature, and the Dark Energy Equation of State

Description: Strong gravitational lens systems with measured time delays between the multiple images provide a method for measuring the 'time-delay distance' to the lens, and thus the Hubble constant. We present a Bayesian analysis of the strong gravitational lens system B1608+656, incorporating (1) new, deep Hubble Space Telescope (HST) observations, (2) a new velocity dispersion measurement of 260 {+-} 15 km s{sup -1} for the primary lens galaxy, and (3) an updated study of the lens environment. Our analysis of the HST images takes into account the extended source surface brightness, and the dust extinction and optical emission by the interacting lens galaxies. When modeling the stellar dynamics of the primary lens galaxy, the lensing effect, and the environment of the lens, we explicitly include the total mass distribution profile logarithmic slope {gamma}{prime} and the external convergence {kappa}{sub ext}; we marginalize over these parameters, assigning well-motivated priors for them, and so turn the major systematic errors into statistical ones. The HST images provide one such prior, constraining the lens mass density profile logarithmic slope to be {gamma}{prime} = 2.08 {+-} 0.03; a combination of numerical simulations and photometric observations of the B1608+656 field provides an estimate of the prior for {kappa}{sub ext}: 0.10{sub -0.05}{sup +0.08}. This latter distribution dominates the final uncertainty on H{sub 0}. Fixing the cosmological parameters at {Omega}{sub m} = 0.3, {Omega}{sub {Lambda}} = 0.7, and w = -1 in order to compare with previous work on this system, we find H{sub 0} = 70.6{sub -3.1}{sup +3.1} km s{sup -1} Mpc{sup -1}. The new data provide an increase in precision of more than a factor of two, even including the marginalization over {kappa}{sub ext}. Relaxing the prior probability density function for the cosmological parameters to that derived from the WMAP 5-year data set, we find that the B1608+656 ...
Date: December 11, 2009
Creator: Suyu, S. H.; Marshall, P. J.; Auger, M. W.; Hilbert, S.; Blandford, R. D.; Koopmans, L. V. E. et al.
Partner: UNT Libraries Government Documents Department

Designing the Ideal Uranyl Ligand: a Sterically-Induced Speciation Change in Complexes with Thiophene-Bridged Bis(3-hydroxy-N-methylpyridin-2-one)

Description: Structural characterization of a mononuclear uranyl complex with a tetradentate, thiophene-linked bis(3-hydroxy-N-methylpyridin-2-one) ligand reveals the most planar coordination geometry yet observed with this ligand class. The introduction of ethylsulfanyl groups onto the thiophene linker disrupts this planar, conjugated ligand arrangement, resulting in the formation of dimeric (UO{sub 2}){sub 2}L{sub 2} species in which each ligand spans two uranyl centers. Relative energy calculations reveal that this tendency toward dimer formation is the result of steric interference between ethylsulfanyl substituents and linking amides.
Date: September 11, 2009
Creator: Szigethy, Geza & Raymond, Kenneth N.
Partner: UNT Libraries Government Documents Department

A tandem-based compact dual-energy gamma generator

Description: A dual-energy tandem-type gamma generator has been developed at E.O. Lawrence Berkeley National Laboratory and Sandia National Laboratories. The tandem accelerator geometry allows higher energy nuclear reactions to be reached, thereby allowing more flexible generation of MeV-energy gammas for active interrogation applications.
Date: November 11, 2009
Creator: Persaud, A.; Kwan, J.W.; Leitner, M.; Leung, K.N.; Ludewigt, B.; Tanaka, N. et al.
Partner: UNT Libraries Government Documents Department

Choke Flange for High Power RF Components Excited by TE01 Mode

Description: A multifaceted program to study high gradient structures and properties of RF breakdown is under way at SLAC. This program includes testing of simplified versions of traveling wave and standing wave structures at 11.4 GHz. [Dolgashev] RF power is fed into these structures using a TE01 mode-launcher. An RF flange is used to connect the mode-launcher to the test-structure. The rf currents flow through either the stainless steel lip on the flange or, in an alternate assembly, through a copper gasket pressed between the same stainless steel lips. In a recent experiment with a single cell traveling wave structure, a flange with stainless steel lips was irreversibly damaged at RF power about 90 MW and {approx}100 ns pulse length. We suggest an alternative flange that does not rely on metal-to-metal contact in the rf power transfer region. The idea is to use an asymmetric choke flange, where the choke grove is cut into a conflate flange on the mode-launcher. The structures themselves will have a simpler, flat conflate flange with rounded corners on the vacuum side. The Vacuum seal is achieved with a Cu gasket between these two flanges above the RF region. We have designed a flange with a choke which is almost field free in the vacuum gasket region, whose technical specifications and RF properties are presented below. Design simulations were conducted using HFSS, a 3D finite element code that solves electromagnetic fields in complex structures. Figure 1 demonstrates the projected physical look of the choke flange, while the table next to it lists the critical parameters. The maximum electric field for in this geometry is on axis at 33.6MV/m for 100 MW input. The electric field near the gasket, meaning at the top of the choke gap is at 125kV/m or 1.25kV/cm. Figure 2 demonstrates the electric ...
Date: December 11, 2009
Creator: Yeremian, A.Dian
Partner: UNT Libraries Government Documents Department

SIAM Conference on Geometric Design and Computing. Final Technical Report

Description: The SIAM Conference on Geometric Design and Computing attracted 164 domestic and international researchers, from academia, industry, and government. It provided a stimulating forum in which to learn about the latest developments, to discuss exciting new research directions, and to forge stronger ties between theory and applications. Final Report
Date: March 11, 2002
Partner: UNT Libraries Government Documents Department